1. Technical Field
The present invention relates to a plastic optical lens and an injection-molding method for manufacturing the same, and more particularly, to a plastic optical lens having a partially indented configuration and an injection-molding method for manufacturing the same.
2. Description of the Related Art
An injection-molded plastic optical lens is formed by injecting a molten plastic material into a mold cavity via a sprue gate after the pieces of the mold have been fully closed together. As the molten plastic material is injected into the mold cavity, the presence of the residual compressed air in the mold cavity at high temperature will scorch and damage the surface of the molded article. Even without damaging the surface of the molded article, the molten plastic material may fill the mold cavity incompletely due to the residual air and thereby adversely affecting the shape of the final molded article formed through a mold replication of the cavity. As there is an increasing demand for high precision lenses for portable mobile devices, it is important to improve the air duct performance during the molding process. In order to prevent the occurrence of the aforementioned problems, a parting plane of a mold is generally provided with an air duct in the form of a shallow groove to allow the air flow access with the external environment so as to facilitate the escape of air from the mold cavity. However, flashes may be formed easily at the exit of the air duct due to the flow of the molten plastic material. JP Patent No. 2008-126611A discloses an air exhaust means that involves incorporation of the air duct as an integral part of the molded article. FIGS. 1A and 1B illustrate a prior art plastic optical lens 1 disclosed in JP Patent No. 2008-126611A. The prior art plastic optical lens 1 comprises an optical effective region 1b and a peripheral region lf that are concentrically formed, wherein the peripheral region 1f has a sprue gate 1g and a flash 15 protruding therefrom and arranged opposite to the sprue gate 1g. As the flash 15 protruding from the peripheral region 1f will adversely affect the assembling of the prior art plastic optical lens 1, mechanical processing is required to remove the flash 15. Accordingly, the processing cost is increased.